The present invention relates to sample containers and more particularly to a repuncturable self-sealing sample container employing an internal collapsible sample bag adapted to retain a dispense sample with minimum evaporation.
Those involved in the art of sample preparation and handling appreciate that solute concentration levels of small amounts of sample can be easily affected by evaporative effects, especially when the sample volume is small, for instance, on the order of microliters. Such small sample volumes undergo appreciable changes in concentration even when dispense into conventional sealed test tubes, as the non-evacuated air in these tubes is sufficient to cause evaporation, and accordingly changes in sample concentration. Sample preparation and handling at these minute volumes would benefit from a container in which evaporation is eliminated or greatly minimized.
A number of different containers have been developed for storing and dispensing fluids from an air-free environment. One particular application has been nursery bottles in which a collapsible bag, typically located within a rigid container, is filled with milk, formula, or other liquid. When topped with the appropriate nipple assembly, feeding from the nipple gradually collapses the bag, thereby minimizing the intake of air. When feeding discontinues, air can enter into the collapsible bag via nipple hole. To prevent the infant""s intake of this air, the nursery bottle may require some compression in order to dispel the air before feeding resumes, or in other embodiments, the nursery bottle itself has a means to collapse the bag in order to prevent the entry of air (see, e.g., U.S. Pat. No. 3,955,698).
Another area (albeit unrelated to the first) in which airtight containers have been developed is in sterile intravenous bags and blood collection structures. U.S. Pat. No. 2,460,641 describes a well-known blood collection apparatus consisting of a sealed, evacuated test tube having a needle pierceable, self-sealing top. Blood is dispensed into the test tube via a holder having two oppositely oriented cannulae. One cannula pierces the membrane of the test tube and the other cannula is connected to an intravenous line. The negative pressure of the test tube operates to extract the blood or other fluid from the intravenous line into the test tube.
When comparing the aforementioned needs to these conventional containers, several disadvantages become obvious. As to the nursery bottle, even the low amounts of air entering to the container would cause an unacceptable amount of evaporation in the present application where milliliters or microliters of sample are being handled. As to the blood container, the evacuated environment would prevent accurate volume regulation of sample dispensed into or extracted from the container. Both containers include appreciable head volumes which could not be effectively evacuated.
What is needed is an improved sample container for retaining small volumes in an extremely low evaporative environment.
The present invention provides for a sample container configured to retain microliters of sample volumes in an extremely low evaporative environment. In one embodiment, the sample container includes a container housing, a repuncturable self-sealing membrane, and a collapsible sample bag. The container housing includes an open end and a hollow interior region. The repuncturable self-sealing membrane configured to self-seal after repeated punctures is engaged in the open end of the container housing and includes an exterior surface exposed to the external environment and an interior surface oriented toward the hollow interior region of the container housing. The collapsible sample bag includes a proximate end that is permanently attached to the interior surface of the repuncturable self-sealing membrane.
Other aspects of the invention will be apparent in view of the following drawings and description of specific embodiments of the invention.